Underground mining of mineral ores, such as coal and hard and soft rock mining requires the developments of underground drives in the form of tunnels. In all hard-rock applications, drive development is achieved through a drilling, charging, blasting, and mucking cycle. In the drilling stage of the cycle, a pattern of holes is drilled into the blind end of the drive. The holes are generally parallel to the drive axis.
In the charging stage, explosive is placed in the drilled holes and connected via a detonating arrangement. In the blasting stage the explosive is detonated, the resulting blast fracturing the solid rock. In the mucking stage a front-end loader digs the fractured rock and removes it for hoisting to the surface via skips. This development cycle is well understood and is currently the most cost effective means of developing drives in hard rock.
An unavoidable consequence of this proven method is rock fracture beyond the desired geometric shape of the tunnel cross-section. This rock fracturing can cause the tunnel roof and/or sidewalls to be unstable. Rock fragments large and small can disengage from the back and sidewalls and fall under the influence of gravity. Particle size ranges from microscopic to cubic meters. Falling particles larger than a tennis ball can prove fatal to personnel.
To protect miners from larger falling particles, a rock bolting/meshing procedure is applied. The process requires drilling holes in the ‘back’ (walls and overhead), and holding square mesh, typically 50 mm×50 mm to 150 mm×150 mm apertures, against the ‘back’. Rock bolts and retaining plates are inserted through the mesh and into the drilled holes. Larger particles are restrained from falling by the rock-bolts and smaller particles are retained or caught by the mesh.
The drill hole depths required for advancement drilling (drilling to extend the length of the tunnel) can be up to 5 meters while drilling in the roof and sides of the tunnel for rock bolts requires a depth of approximately 3 meters. Drilling is generally carried out using a percussive rock drill mounted to a slide. The drill steel (drill bit) is supported at one end by the drifter (drill) and at the other end by a drill guide. For long drill steel, a centre steady is often required. The total length of the drill slide assembly required to drill a 5 meter hole is about 6.5 meters being made up of the drill steel, the drifter, a hose guide spool typically mounted behind the drifter and the drill steadies. Typical mining cross sections range from 3 meters×3 meters to 6 meters×6 meters. It is therefore difficult to use a drill slide mechanism of a set length to drill the advancement holes and the rock bolt holes.
One solution to overcome this is providing two different machines, each fitted with appropriate length sides or alternatively by using a single machine fitted with a split feed. A split feed consists of one slide mounted on another slide allowing the length of the slide to be adjusted. These split feeds are quite complicated mechanisms that require high maintenance and are also mechanically quite complicated and unreliable.
A further prior art embodiment is to use a drill slide that uses a telescoping feed arrangement. This telescopic arrangement wears very rapidly as the sliding surfaces are under load as the elongate telescopic member is jammed against the rock face while the drill is moving. Another problem is that the telescoping elongate member is also at the rock face where all of the ground rock from the holes discharges. This discharging rock rapidly wears the telescope and makes such an arrangement costly and unreliable.
The present invention seeks to provide a drill slide for a drilling apparatus that overcomes at least one of the disadvantages of the prior art.